Separation of matter is one of the oldest methods in experimental research. Many solutions were made to fit the devices to the different sizes of vessels and variations of the openings (U.S. Pat. No. 2,703,670A, CH 241194A, U.S. Pat. No. 2,331,234A, WO 2009096790A1, US 20130306576A1).
All solutions have the same characteristic, they are loosely placed on the opening of the container, which allows the pressure exchange between the separation device and the laboratory container thereby facilitating the free flow of the liquid. The varying diameters of the vessels is typically bridged by giving the outflow a conical shape (funnel shape).
WO 2009096790 A1, where the filter is provided with a plurality of supporting edges which fit to the outside of a vessel. The filter rests via the supporting edges on the vessel. Filters of this kind which simply sit on top of a vessel (tube) tend to tilt over.
The separation of particles and molecules by means of filtration is an increasingly more important tool in experimental research and has led during the last decades to new and revolutionizing applications like sterile filtration of media, dialysis or desalination of salt water.
With the use of particles as the carrier of molecule specific binding moiety, filters with greater mesh size are needed. Therefore, a 20 μm mesh is commonly used in medical devices for immune aphaeresis. But also in biological/medical research have filters with mesh sizes in μm range found a wide usage for separation purposes.
WO2012066503 reveals a container for selective transfer of specimens of biological material by using a separation system hanging a centrifugation. EP0237674A2 also describes a filter which hangs inside the centrifuge basket.
WO 1993001271 describes a filter hanging inside a vessel leaving no space between the side walls of the filter and the container, which impairs the exchange of pressure when the filter is filled with fluid. This can impair with the free flow, especially if the specimen is of viscous consistence. Then the filters have to be lifted up manually to allow the air exchange.
The volume of the filter systems described above the sieve, is limited and mostly even is too small to hold the sample volume of a standard tube. A constant refill is necessary during filtration.
But the small size of the filter/mesh area in devices for laboratory use is the result of the practical laboratorial work. Only a limited amount of sample material is needed, all necessary other buffers and disposables are minimized, rack space is reduced, more samples can be handled parallel, and, at the end, costs are reduced.
EP2664367A1 describes a cell strainer which is compatible with tubes of different opening sizes, i.e. fits on at least both the standard 15 ml and 50 ml laboratory tubes. The strainer consists of two parts, an “upper portion” which is the original strainer, and a “lower portion” which is an adaptor between the strainer and the standard tubes.
The lower adaptor portion has shoulders or flanges which define at least one recess for air exchange. It is designed to fit into the openings of different sizes by having shoulders or projections which have the diameter of the opening of a first tube, and a second section having an inner and outer wall as a holder for the neck of a second tube. The cell strainer according EP2664367A1 can be used for the removal of cell aggregates or large particles after tissue dissociation or from blood samples of up to 50 ml to obtain uniform single-cell suspensions. The design of the filters allows improved ventilation during filtration, and so avoids clogging of the filter. But the upper parts (the strainer) cannot be used separately from the lower (adapter) part. They cannot be inserted in centrifuge tubes. They cannot be flipped around on a standard tube to backwash the filter surface. They cannot be connected to a vessel which contains samples.
There is a need for a versatile filter apparatus which provides sufficient filter efficiency but is also compatible with small tube sizes; filters which can also be used inside a centrifuge tube, filters which can be used in both flow directions and can be connected to a sample reservoir, and, last but not least, provide a reaction room to work on/with the separated particles.